How Mary went blind: A 'Little House on the Prairie' investigation

This book of the series contains the shocking news that Mary Ingalls has gone blind.

Credit Little House Books

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Hear a longer interview with Sarah Allexan

The Little House on the Prairie books by Laura Ingalls Wilder have entertained kids for almost seventy five years, while teaching them a little about what life was like for pioneers during the late 1800s. While the books were published as fiction, most of the story was taken from Wilder’s own childhood. One of the biggest turning points in the books is when Laura’s older sister Mary goes blind after getting scarlet fever. But an article recently published in the American Academy of Pediatrics argues that scarlet fever did not cause Mary’s blindness at all.

One of the authors of the study was Kalamazoo College graduate and first-year University of Colorado medical student Sarah Allexan.

“We consulted an ophthalmologist on our paper, Jerry, and he told us that he looked through a lot of things and it’s hard to find an ocular manifestation of scarlet fever," says Allexan. "If it were to somehow get into the eye, it would have caused a lot of external damage and you would be able to tell that that person had had scarlet fever. But I mean, needless to say there’s no recorded things of this actually happening. A lot of things we were able to rule out due to the fact that in Laura’s book she wrote that Mary’s eyes were still beautiful, they were blue, and you couldn’t tell anything from the outside that her eyes had had this problem.”

Allexan says even the smallest clues helped the research team narrow down what caused Mary to go blind.

“We found this photo that had been taken relatively close to the time that she had gone blind. And we could see that the folds around her nose—the nasal labial folds—were both intact and so we could presume from that that it hadn’t been a stroke since those muscles weren’t still paralyzed," she says. "That was just a useful visual for us since there isn’t much that we could actually see.”

But if it wasn't scarlet fever, what was it? Allexan has the answer:

"We think the most likely possibility is meningoencephalitis, which is just an inflammation or infection of the tissues surrounding the brain and spinal cord. And due to the eye and the optic nerve being so closely intertwined with that, is what led us to believe that that would be the most near association. And there’s many different ways you can acquire a viral meningitis. You can get it from a virus. You can get it from the herpes simplex virus which is just anything simple as cold sores…if the virus happens to get into your eye. Or you could get it from Lyme disease, ticks, mosquitos—different vectors that will bear a virus.”

Allexan says the brain infection was one of the four leading causes of blindness listed on the 1890 Census, as was scarlet fever. Though we’ll never truly know why Little House on the Prairie misdiagnosed Mary, Allexan says scarlet fever also played a large role in other 19th century literature—like Little Women by Louisa May Alcott and Mary Shelley’s Frankenstein.

“We don’t want it to come across as ‘Laura was wrong’ or anything like that," says Allexan. "I think it was a really important literary device that she used, because when we look back through stuff she…all of her memoirs didn’t say scarlet fever until the very end. So, what we’re guessing is that it was really and editing thing because she had sent it to the editors about three times. There’s three different copies that we looked through of Pioneer Girl. And then they decided towards the end ‘Oh, we’re going to make this a children’s book. We’re not going to make this an autobiographical book.’ And so we’re kind of guessing that it seemed like a much more popular disease. Many people had people that they knew that had gone through that or had died from scarlet fever in the recent past. And so, it seemed like an almost poetic way of making Mary go blind.”

Sarah Allexan is a medical student at the University of Colorado and a Kalamazoo College alum. She’s one of the authors of the medical article “Blindness in Walnut Grove: How Did Mary Ingalls Lose Her Sight.”